A COMPARISON OF MERISTEMS AND UNEQUAL GROWTH OF INTERNODES IN VINY MONOCOTYLEDONS AND DICOTYLEDONS

The distribution of meristematic activity and cell length in the growing internodes of seven species of dicotyledonous vines and three species of monocotyledonous vines is described. In Schlegelia, Ipomoea, Mucuna, Passiflora, Ficus, Thunbergia alata, Dioscorea, Smilax, and Vanilla the loss of meristematic activity proceeded from the base to the top of the internode. The absence of isolated meristematic regions is typical of the uninterrupted meristem. In Thunbergia grandiflora a small peak of residual meristematic activity is located at the base of the internode, which is typical of the intercalary meristem. The same region of the internode is swollen and functions as a pulvinus. The young internodes of the seven dicotyledonous vines and an additional eight species of monocotyledonous vines with uninterrupted meristems were marked into three segments for growth studies. The upper part of the internode grew more rapidly and for a longer time than the basal part of the internode, except in T. grandiflora. The relative amounts of unequal growth in various species differed widely. Greater growth of the upper region was not correlated with comparable increases in final cell length in the upper region. It is concluded that the uninterrupted meristem is a common feature of shoot extension in many monocotyledons and dicotyledons.